AssetDatabase.ImportPackageを連続で呼び出す

SequentialImport.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEditor;
using System;

public class ImportPackageList : ScriptableSingleton<ImportPackageList>
{
    public List<string> list;
}

public class Import
{
    [MenuItem("Import/テスト")]
    static void ImportTest()
    {
        ScriptableSingleton<ImportPackageList>.instance.list = 
            new List<string> { @"C:\Users\Desktop\1.unitypackage", @"C:\Users\Desktop\2.unitypackage" };
        AssetDatabase.importPackageCompleted += Complete;
        ImportTest2();
    }

    static void ImportTest2()
    {
        if (ScriptableSingleton<ImportPackageList>.instance.list?.Count <= 0)
        {
            return;
        }

        AssetDatabase.ImportPackage(ScriptableSingleton<ImportPackageList>.instance.list[0], true);
        ScriptableSingleton<ImportPackageList>.instance.list.RemoveAt(0);
    }

    public static void Complete(string name)
    {
        Debug.Log($"{nameof(Complete)}/{name}");
        ImportTest2();
    }
}

public class ImportProcessor : AssetPostprocessor
{
    static void OnGeneratedCSProjectFiles()
    {
        Debug.Log("call");
        Import.Complete("");
    }
}